The outer segment of rod photoreceptor cells consists of a plasma membrane that surrounds a highly organized stack of discs. The long term goal of this research program is to identify and characterize rod outer segment (ROS) plasma membrane proteins and define their role in phototransduction, outer segment structure and stability, metabolic and regulatory and retinal degenerative disease including retinitis pigmentosa. The specific aims are: (1) to study the structure-function relationships of the rod cGMP-gated channel: studies will include (a) analysis of the subunit composition and subunit-subunit interactions of the channel complex; (b) defining the role of the glutamic rich region (GARP) of the beta-subunit in outer segment structure; and (c) elucidating mechanisms that regulate the activity of the channel as part of the phototransduction and adaptational processes; (2) to study the structure, function and regulation of the rod Na+/Ca2+-K+ exchanger: studies will be directed toward determining the role of the large intracellular and extracellular domains of the exchanger in: (a) cation transport function; (b) Ca2+-mediated regulation of exchange activity; and (c) protein-protein interactions that may serve to stabilize the outer segment structure; and (3) to identify and characterize two calmodulin-binding proteins of 67 kDa and 160 kDa in ROS as a first step in determining their role in the Ca2+-dependent regulation of outer segment processes. A variety of current biochemical, molecular biological, cell biological, immunochemical and biophysical methods will be employed along with a unique panel of highly specific monoclonal and polyclonal antibodies and cDNAs to outer segment proteins. The results of these studies should provide new insight into the structure, function and regulation of the cGMP-gated channel, the Na+/Ca2+-K+ exchanger and calmodulin-binding proteins of rod segments and define their role in retinal degenerative diseases.